FIG. 1.1 is a block diagram of a wireless receiver for receiving an analog AV signal in the prior art. A wireless receiver 10 comprises a radio frequency (RF) receiver 11, a zero intermediate frequency (zero-IF) direct down converter 12, an In-phase/Quadrature (I/Q) imbalance calibrator 13, and a baseband demodulator 14. The RF receiver 11 receives an RF AV signal that comprises an RF video signal and an RF audio signal. The RF video signal and the RF audio signal are applied to an analog TV system, and are respectively within different frequency bands and have different central frequencies.
FIG. 1.2 shows a typical I/Q imbalance calibrator 13 in the prior art. It represents a schematic view with comparison between a down-converted baseband video and audio signals and ideal signals. When the foregoing baseband video signal and the baseband audio signal are directly down-converted via the zero-IF direct down converter 12, in-phase and quadrature component imbalances often occur. As shown in a dotted frame 17-1, suppose that in-phase components of an ideal baseband video/audio signal have a central frequency f0 in the frequency domain. The imbalance of the in-phase components of the baseband video/audio signal has a mirror signal symmetric to the frequency f0, where the mirror signal has a central frequency −f0 in the frequency domain. As shown in a dotted frame 17-2, the quadrature components of an ideal baseband video/audio signal have a central frequency −f0 in the frequency domain. The imbalance of the quadrature components of the baseband video/audio signal has a mirror signal symmetric to the frequency −f0, where the mirror signal has a central frequency f0 in frequency domain. More specifically, since the RF video signal and the RF audio signal are within different frequency bands and have different central frequencies, the down-converted baseband video and audio signals are also within different frequency bands and have different frequencies. In practical applications, the down-converted baseband video and audio signals respectively have different I/Q imbalance values. Therefore, a solution is needed to solve the foregoing problem of imbalances of signals that are down-converted. However, with respect to signals within two different frequency bands, the foregoing conventional structure of calibrator and calibrating method only perform identical calibration based on the down-converted mixed signals, fails in specifically calibrating the video signal or the audio signal, and thus creates an un-ideal calibrating effect.
In view of the foregoing issues, a calibrator for calibrating an AV signal and a method thereof are provided to solve the foregoing problems of the I/Q imbalance calibrator 13 of the conventional wireless receiver 10 and the method thereof.